JPH0572349B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a method for producing unfired bricks for constructing the inner wall of a hot metal container such as a mixer car or a hot metal pot for storing hot metal and performing preliminary treatments such as desiliconization, dephosphorization, and desulfurization. It is related to. <Prior Art> The inner wall of the hot metal container is significantly eroded and damaged by contact with the agitated flow of hot metal and active slag during the preliminary treatment of desiliconization, dephosphorization, and desulfurization of hot metal. Therefore, the refractory bricks used to construct the inner wall are Al ₂ O ₃ −
SiC-C based unfired bricks have generally been used. Conventionally, the method for manufacturing Al ₂ O ₃ -SiC-C based unfired bricks involves kneading phosphorous graphite with a particle size of 100 μm or less as a carbon source into an alumina raw material and silicon carbide together with a binder, and forming it into a compact. The material was formed into a rectangular parallelepiped or a similar shape by strongly pressurizing it from the short axis direction, and then heat-treated. the result,
The thermal conductivity in the long axis direction is 8 kcal/m·h·°C or more. When bricks obtained by this manufacturing method are used in hot metal containers, the transfer of heat to the back side increases, resulting in a significant drop in hot metal temperature.In the subsequent treatment process, the pig iron yield decreases and the basic unit of auxiliary raw materials increases. do. As an improvement to the above manufacturing method, the particle size of graphite was reduced to 20 μm.
JP-A No. 62-56354 discloses one defined as less than m. However, it is not possible to reduce the thermal conductivity to 6 kcal/m·h·°C or less just by making the graphite finer, and it is necessary to add a heat source because the temperature of the hot metal decreases during the preliminary treatment. <Problem to be solved by the invention> In the method for producing Al ₂ O ₃ -SiC-C-based unfired bricks, when scaly graphite refined to 40 μm or less is used, the thermal conductivity is approximately 2 kcal/m・h・℃. descend. If the decrease in thermal conductivity was only due to the miniaturization of scaly graphite, the temperature of the hot metal contained in the hot metal container would still drop during treatment, making the pretreatment operation complicated, such as adding an increased amount of heat source. Furthermore, there is a large difference in specific gravity between the alumina raw material and graphite flakes, and if the particle size of graphite flakes is made smaller, the specific surface area increases, so the conventional method described above requires a large amount of binder. Therefore, dense and homogeneous Al ₂ O ₃
-SiC-C unfired bricks cannot be obtained. <Means for solving the problems> The present invention provides an Al ₂ O ₃ -SiC-
By improving the manufacturing method of C-based unfired bricks, we obtained dense and homogeneous Al ₂ O ₃ -SiC-C-based unfired bricks with a thermal conductivity of 6 kcal/m・h・℃ or less, which can be used in hot metal containers. The aim is to extend the service life of the inner wall of the molten metal and to significantly reduce the load on hot metal pretreatment operations. The features of the present invention include 10 to 30% by weight of alumina raw material with a particle size of less than 125 μm, the balance being 60 to 94% by weight of an alumina raw material with a particle size of 125 μm or more, and 3 to 30% by weight of silicon carbide.
Of the raw materials consisting of 20% by weight and 3 to 20% by weight of scaly graphite with a particle size of 40 μm or less, an alumina raw material with a particle size of less than 125 μm, silicon carbide, scaly graphite, and a binder are pre-kneaded, and the pre-kneaded product is mixed with granules. This is a method for producing unfired bricks for hot metal containers, which comprises adding and kneading alumina raw materials having a diameter of 125 μm or more, followed by shaping and heat treatment. <Function> The inner wall of a hot metal container such as a pig iron mixing car is constructed by stacking bricks with their long axis direction aligned with the thickness direction of the inner wall, that is, one end face in the long axis direction of the bricks (parallel to the cross section) is the working surface of the inner wall, and the cross section of the brick is always the working surface. The reason that the thermal conductivity of the bricks containing flaky graphite is higher in the long axis direction than in the short axis direction is that the flaky graphite becomes parallel to the long axis direction due to strong pressure compression from the short axis direction during brick molding. This is caused by lining up. Therefore, as a means to reduce the orientation of flaky graphite, if the particle size of flaky graphite is made smaller than other alumina particles, etc., the flaky graphite will surround the alumina particles, etc., and the long axis of the brick will be reduced. The orientation of the direction is reduced, and the thermal conductivity can be reduced. Furthermore, in order to ensure this, if the particles are adhered to alumina particles or the like by preliminary kneading, the orientation will be almost eliminated. Moreover, the amount of binder can be reduced by preliminary kneading, resulting in excellent physical properties. In order to reduce thermal conductivity by almost eliminating the orientation of scale graphite as described above, and to make dense and homogeneous unfired bricks for hot metal vessels by adding a small amount of binder, the above raw materials are processed as follows. Perform preliminary kneading and post-kneading. (1) Pre-kneading (a) Alumina raw material: 10 to 30 parts by weight with particle size
Less than 125 μm (b) Silicon carbide: 3-20% by weight (c) Scale graphite: 3-20% by weight less than 40 μm (d) Binder: When 2-6% by weight is kneaded in an outer layer, alumina particles, etc. As a result of adhering and arranging the fine scale graphite around it in a matrix, the fine scale graphite is uniformly dispersed and has almost no orientation. (2) Post-kneading (a) Pre-kneaded product of (1) (b) Alumina raw material: By kneading the remaining 70 to 90% by weight of the above (1) with a particle size of 125 μm or more, a uniform scale of graphite can be obtained. Dispersion and non-directionality are maintained, and the aggregate is evenly dispersed and mixed. Even if the kneaded product obtained through steps (1) and (2) is molded into bricks as described above, the uniform dispersion and non-directionality of the graphite scales after kneading are not affected by the direction of strong pressure during molding and hardly change. As a result, the thermal conductivity in the long axis direction of the brick was reduced by 2 to 4 kcal/m・h・℃, and by 6 kcal/m・h・℃.
It can be made below m・h・℃. The alumina raw materials used in the present invention include:
These are fused alumina, sintered alumina, sillimanite, bauxite, etc., and the Al ₂ O ₃ content in the raw materials is
The content is preferably 50% by weight or more from the viewpoint of corrosion resistance. The amount of the alumina raw material used is 60 to 94% by weight; if it is less than 60% by weight, corrosion resistance cannot be sufficiently exhibited, and if it exceeds 94% by weight, the body spalling property is poor, which is not preferable. In addition, the blending ratio and particle size of this alumina raw material in the above (1) preliminary kneading are 10 to 30% by weight, and 125 μm.
less than As a result, during the preliminary kneading, fine scale graphite is adhered to and evenly dispersed around the alumina particles, etc., thereby obtaining a dense brick with excellent corrosion resistance. Therefore, if particles with a particle size of 125 μm or more are added, a dense product with excellent corrosion resistance cannot be obtained. In addition, the above formulation is also less than 10% by weight, or
If it exceeds 30% by weight, a dense product with excellent corrosion resistance cannot be obtained. Silicon carbide has the effect of suppressing the oxidation of graphite and making graphite exhibit high corrosion resistance and high spalling resistance.
The amount used is 3-20% by weight. If this amount is less than 3% by weight, the effect of suppressing graphite oxidation will not be sufficiently exhibited, and if it exceeds 20% by weight, corrosion resistance will be poor. Scale graphite contributes to corrosion resistance and spalling resistance by being difficult to wet with slag, and the particle size used is 40 μm or less, which is close to the scale thickness that almost eliminates the orientation of scale graphite. The amount used is 3 to 20% by weight, and if it is less than 3% by weight, corrosion resistance and spalling resistance will be poor, and if it exceeds 20% by weight, mechanical strength will decrease and wear resistance will be poor. If a large amount of scaly graphite is used, the amount of silicon carbide is reduced so that the thermal conductivity is 6 kcal/m·h·°C or less. For example, 10% by weight of scaly graphite
In the case of 20% by weight or less of silicon carbide and scaly graphite.
In the case of 15% by weight, it is preferable to adjust the silicon carbide content to 10% by weight or less. Metal powders such as Al, Si, Mg, glass substances, etc. can be added to the above raw materials, thereby further improving the oxidation resistance. The binder is preferably a resin-based one, and a phenol resin that hardens by heat treatment is suitable. A portion of the binder can also be added during post-kneading after pre-kneading. By lining the entire hot metal part or furnace bottom of a hot metal pretreatment vessel such as a pig iron mixer or a hot metal pot with the unfired bricks obtained as described above, or by lining all but a part of the furnace bottom, A decrease in hot metal temperature can be suppressed. <Examples> The present invention will be explained in detail below using examples. Examples 1 to 4 Alumina raw materials with a diameter of less than 125 μm shown in Table 1,
Silicon carbide, scaly graphite, and phenolic resin were pre-kneaded using a shear kneader. The particle size of this pre-kneaded material
An alumina raw material with a diameter of 125 μm or more was added and kneaded using a pressure kneader. This kneaded product was molded using a friction press, and the molded product was heat-treated at 300°C for 10 hours to obtain unfired bricks. Table 1 shows the physical properties of the thus obtained unfired bricks and test results such as spalling resistance and corrosion resistance. In addition, spalling resistance is determined by the elastic modulus before the test and after immersing the sample in hot metal at 1500℃ for 3 minutes.
The elastic modulus was measured after lifting and air cooling, and this was repeated on the third floor, and the retention rate was calculated from the ratio of the elastic modulus before the test to 100. In addition, the corrosion resistance was determined to be 1450 by the rotating slag test method.
℃ for 5 hours. Slag composition is SiO ₂ 46% by weight,
The composition used contained 6% by weight of CaO, 4% by weight of Fe ₂ O ₃ and 4% by weight of MnO ₂ . The results are based on Comparative Example 1.
Expressed as a ratio of 100.

【table】

[Table] From the results in Table 1, 10 to 30% by weight of the total amount of alumina raw material has a particle size of less than 125 μm, and the particle size is less than 125 μm.
Examples 1 to 4 in which graphite scales with a particle size of 20 μm or less were pre-kneaded had significantly lower thermal conductivity than Comparative Example 1 in which graphite scales with a particle size of 100 μm or less were used. Comparative Example 2 uses flaky graphite with a particle size of 20 μm or less, but because it is not pre-kneaded, the thermal conductivity is
6 kcal/m・h・℃ or less, and in Comparative Example 3, the alumina raw material with a particle size of less than 125 μm was
% by weight, and even if pre-kneaded, a dense product cannot be obtained and the corrosion resistance is poor. Furthermore, in Comparative Example 4, an alumina raw material having a particle size of 125 μm or more was added to the preliminary kneading, and it was observed that a dense product could not be obtained and the corrosion resistance was poor. Example 5 As a result of using the bricks of Example 2 and Comparative Example 1 in the pig iron bath of a pig iron mixing car, the hot metal temperature of the brick of Example 2 was 1398°C, whereas that of Comparative Example 1 was 1390°C. ℃, and the drop in hot metal temperature could be suppressed by 8℃. <Effects of the Invention> As explained above, the method for producing unfired bricks for hot metal containers of the present invention includes preparing an alumina raw material with a particle size of less than 125 μm, silicon carbide, scaly graphite with a particle size of less than 40 μm, and a binder. This is a method of kneading, adding an alumina raw material with a particle size of 125 μm or more to this pre-kneaded product, kneading, shaping, and heat-treating.This method almost eliminates the orientation of graphite scales and significantly reduces thermal conductivity. I was able to do it. As a result, it has become possible to suppress the temperature drop of hot metal and significantly reduce the load on pretreatment operations.

Claims (1)

[Claims] 1. Alumina raw material 60 to 94 with 10 to 30% by weight of particles with a particle size of less than 125 μm and the remainder having a particle size of 125 μm or more
Among the raw materials consisting of 3-20% by weight of silicon carbide and 3-20% by weight of scaly graphite with a particle size of 40 μm or less,
Alumina raw material with a particle size of less than 125 μm, silicon carbide,
A method for producing an unfired brick for a hot metal container, which comprises pre-kneading graphite scales and a binder, adding an alumina raw material having a particle size of 125 μm or more to the pre-kneading mixture, and then shaping and heat-treating the mixture.